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SiO_2薄膜是光学薄膜领域内常用的重要低折射率材料之一。在文中研究中,通过测量薄膜的椭偏参数,使用非线性最小二乘法反演计算获得薄膜的光学常数。采用离子束溅射和电子束蒸发两种方法制备了SiO_2薄膜,在拟合过程中,基于L_8(2~2)正交表设计了8组反演计算实验,以评价函数MSE为考核指标。实验结果表明:对IBS SiO_2薄膜拟合MSE函数影响最大的为界面层模型,对EB SiO_2薄膜拟合MSE函数影响最大的为Pore模型。同时确定了不同物理模型对拟合MSE函数的影响大小和反演计算过程模型选择的次序,按照确定的模型选择次序拟合,两种薄膜反演计算的MSE函数相对初始MSE可下降35%和38%,表明拟合过程模型选择合理物理意义明确。文中提供了一种判断薄膜物理模型中各因素对于薄膜光学常数分析作用大小的途径,对于薄膜光学常数分析具有指导意义。
SiO 2 film is one of the most important low refractive index materials commonly used in the field of optical films. In the study, the optical constants of the films were obtained by measuring the ellipsometric parameters of the films and using the nonlinear least square method. SiO_2 thin films were prepared by ion beam sputtering and electron beam evaporation. In the fitting process, 8 groups of inversion calculation experiments were designed based on the L_8 (2 ~ 2) orthogonal table, and MSE was used as evaluation index. The experimental results show that the most influential factor for the MSE function of the IBS SiO 2 film is the interface layer model, and the Pore model is the most influential for the EBE SiO 2 film fitting MSE function. At the same time, the influence of different physical models on the fitted MSE function and the order of model selection for inversion calculation process are determined. According to the determined model selection order, the MSE function calculated by the two thin films can be reduced by 35% compared with the initial MSE 38%, indicating that the fitting process model to choose a reasonable physical significance. The paper provides a way to judge the effect of various factors on the optical constants analysis of the thin film physical model, which is of guiding significance for the optical constant analysis of the thin film.